1. Field of the Invention
Embodiments of the invention generally relate to a device for continuous coating of a strip-like substrate in a vacuum, especially for manufacturing coating patterns on the substrate with a printing roller and a backing roller between which the substrate is transported.
2. Description of the Related Art
The invention furthermore relates to devices for continuous coating of a strip-like substrate in a vacuum wherein in a working position adjustable with a servo unit, the printing roller and the backing roller are in operative connection with one another by means of which a coating or release agent is transferable to the substrate via the printing roller.
Devices of this kind are used especially in coating installations for continuous evaporation or sputtering of foil strips and webs in a vacuum. In special embodiments, they serve for example in the production of coating patterns on the strip-like substrate that are formed either in longitudinal stripes or across the full coating width of the substrate to be coated. These coating patterns, also called pattern structures, have in some cases sections that are coating-free that can be realized by different coating masks. In pattern masking, a special oil-masking technique, when this technology is applied to coating technology, the coating-free sections are masked by means of a release agent, mostly oil, before the coating material is applied to the substrate. The prior art, as known from, e.g. DE 197 32 929 A1, DE 43 10 085 A1 and DE 41 00 643 C1, consists in feeding the strip-like substrate, e.g. a foil strip between a printing roller and a backing roller, with the printing roller having projecting pattern elements, which are wetted with an oil film, such that an oil pattern is applied to the strip-like substrate during roll-off of the printing roller. The oil-patterned strip is subsequently coated by sputtering or evaporation, whereby the, e.g., metallic coating material deposits on the oil-free sections of the substrate as a layer of metal and the masked areas are protected from the condensing metal, such that the result is selective metallization pattern on the substrate. Capacitor foils are made in this way, for example.
Setting of the printing roller and the backing roller relative to each other in a working position in which the release agent is transferred to the substrate occurs by means of a servo unit, which has a guideway for the printing roller or the backing roller, an adjustable stop of the guideway as well as one or more hydraulically or pneumatically actuated pressure cylinders for offsetting the rollers. When the pressure cylinders are actuated, for example, the printing roller is moved axially parallel with the backing roller toward the latter. Likewise, the backing roller can also be moved by means of the pressure cylinder toward the printing roller. The adjustable stop of the guideway limits the respective pressure cylinder stroke at an end position, which corresponds to the precise working position of the printing roller relative to the backing roller. The position of the stop is predetermined by a manual adjusting screw corresponding to the parameters of the respective pattern process. Thus, the rollers, under variable parameters, are aligned with each other with the greatest precision in the working position required in each case. The position selected for the stop is fixed with a clamping screw. Counter-pressure cylinders of the servo unit that are directed against the pressure cylinders move the printing roller from the working position into a resting position in which the printing roller and the backing roller are disconnected from each other in order that, for example, a sleeve of the printing roller may be exchanged for the projecting pattern elements. Exchangeable sleeves make it possible to produce strip-like substrates in all kinds of patterns. After a sleeve change, the working position has to be reset in order that correct alignment and the appropriate contact pressure of the printing roller against the backing roller may be ensured. To this end, the locator of the stop is released by hand and the pressure cylinder is actuated until the printing roller rests flush against the backing roller. Subsequently, the stop is adjusted by means of the adjusting screw in accordance with the executed pressure cylinder stroke and located in position with the clamping screw. The coating installation is then sealed vacuum-tight, evacuated and test coating is performed so that the dimensional accuracy of the coating pattern may be checked. The precision with which the working position of the rollers has been set by the servo unit can be judged only from the coated substrate. If necessary, the setting process must be repeated after venting of the coating installation, and more precisely until the coating pattern is of the desired quality. Precision setting of the working position of the printing roller against the backing roller after a change in parameters of the pattern process, such as after a sleeve change, therefore entails a high outlay on time, which can amount to more than one working day, depending upon the situation. In addition, this time- and labor-intensive setting-up causes substantial production downtimes, which impair the economics of the coating installation.
The object of the invention is therefore to overcome the disadvantages of the prior art and to improve the adjustability of the generic device. This object is achieved in accordance with embodiments described herein by the servo unit having a controllable servo motor for adjusting the working position.